[Halld-pid] Time-of-Flight Meeting Minutes, January 10, 2017

[Mark Ito]

Folks,

Please find the minutes below and at 
https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_10,_2017 
.

   -- Mark

______________


    GlueX TOF Meeting, January 10, 2017, Minutes

Present:

  * *FSU*: Paul Eugenio
  * *JLab*: Thomas Britton, Brad Cannon, Mark Ito (chair)


      Lucite Shield Results

Paul led us through his logbook entry 
<https://logbooks.jlab.org/entry/3448871> (shown below) tabulating the 
results of the test of a Lucite shield for the counters closest to the 
beamline. Data were taken at the end of the Fall run. Substantial rate 
reduction was observed with the TOF discriminator scalers. For example, 
the 2.25 inches of Lucite (17% of a radiation length) reduced the rate 
in S:21 by about 35% and that in S:22 by about 45%, independent of the 
beam rate used in the measurement.

TOF-Shield-Study-Fall2016-4.png 
<https://halldweb.jlab.org/wiki/index.php/File:TOF-Shield-Study-Fall2016-4.png> 


We concluded that the Lucite would not do harm to the TOF measurement 
and gives a substantial rate reduction, reducing the current load on the 
last dynode of the PMTs. The hypothesis is that low energy electrons and 
positrons are getting ranged out in the additional shielding. Now that a 
significant effect has been observed, the next step is to see what a 
Monte Carlo study says. Pending results of that study, the proposal is 
to leave the configuration of shielding used in the study in place for 
the next run. It appears to be doing more good than harm.


      PMT Testing

Paul drove the 25 PMTs to be tested down to FSU. Five were retained at 
JLab for studies. Ashley Ernst, an FSU grad student, will execute the 
testing procedure 
<http://hadron.physics.fsu.edu/wiki/index.php/Photomultiplier_tubes>.


      PMT Voltage Scan Analysis

Brad has been hampered in his efforts by the Lustre disk problems at 
JLab. This remains work in progress.


      Collaboration Meeting

Brad will give the TOF report at the upcoming meeting.


-- 
marki at jlab.org, (757)269-5295

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